Some effects of the gonadotrophines releasing hormone (GnRH) on the late puerperium of milking cows

Abstract

One hundred thirteen Holstein breed dairy cows on the 35^tn day after parturition (AP) were used. Sixty of these cows formed group I (GI) that was treated with 250 mg of GnRH intramuscularly and 53 cows formed group II (GII), the control group, ijected with phisiologic solution. All animals were examined through rectal palpation for signals of uterine involution as well as for ovarian function on the following days: 28^tn, 32^tn, 35^th, 39/40^th, 42/45^th, and 50^th. On the 35^th day AP the cows in GI were given GnRH and the cows in Gil were given 5 ml of physiologic solution. After treatment, all animals were examined twice a day for heat. The results indicated that: a) The interval treatment/ovulation in days was practically the same in the two groups, although 32,3% of animals in GI presented exterior signals of the first estrum post treatment, with only 7,2% of animals giving the same answer in Gil (P < 0.05). Also, 73,4% of GI cows showed ovulation. This proportion was only 37,7% in Gil (P < 0.01). Finnaly, GnRH was considered efficient on the ovarian follicular development, since 85,0% of cows in GI presented good development against 47,1% of cows in Gil (P < 0.01).